I am working on a BOM for this, and have a few questions.
For the LEDs, what forward drop? I see Hesener used green ones, so 1.7V?
If so is this okay: 351-3242-RC Xicon | Mouser
For the 12V zener, is this mouser part okay: 771-BZX79-B12133

I will share the project when it is done, in case there are others with boards but no parts.

For the RIAA caps, it seems FKP and not MKP are the way people are going?
Also for those that have sorted succesfully, what make are you 337/327s?

I think the Zeners are ok. You choose super bright Leds. The voltgae is ok but Frans lets them work on very low current so they may not light up. I use low current ( 2mA ) green Leds, diffuse. Clear will worlk too i think but is has to be a low current Led.